The invention pertains to a rotary drum with a rolling body for cleaning the interior of the rotating drum. The rolling body arrangement includes a stationary feed end for the material to be treated, a mounting device for mounting the rolling body arrangement on to the feed end of the rotary drum and a rotary bearing that allows the rolling body to roll on the inner side of the rotary drum wall and which connects the rolling body to the mounting device.
Rotary drums of this type are primarily used in chemical processes that are, in particular, carried out at elevated temperatures, e.g., carbonization processes. In this case, the operating temperatures in the interior of the drum that is externally heated in most instances may lie on the order between 600xc2x0 C. and 850xc2x0 C. Naturally, the operating temperatures may also be higher or lower. So-called rolling bodies are used for continuously removing deposits that are caked, encrusted or the like on the interior of the rotary drum, wherein said rolling bodies roll on the interior of the rotary drum due to its rotation and entirely or partially remove or prevent an extensive built-up of such deposits on the inner wall of the rotary drum with cleaning strips provided on the outside of the rolling bodies.
In the rotary drum known from DE 27 39 148 C3, some oblong scraping devices are coupled at distances one behind the other by chains. This allows pendulum movements only, but no rolling/rotating cleaning movements for any of the scraping devices.
In the rotary drum known from WO 9839611, which is internally cleaned by means of rolling bodies, the typically non-cylindrical and cylindrical inner wall regions of the feed end of a rotary drum are cleaned with a combination of rolling bodies, the cleaning surfaces of which are arranged at an angle relative to one another. This cleaning arrangement is preferably realized in the form of several successively coupled rolling bodies that are equipped with a ball joint on their ends that are situated on the feed side in order to allow the rolling motion. However, practical tests demonstrated that these cleaning arrangements can be additionally improved in order to achieve a superior cleaning of the rotary drum interior in the end region on the feed side and a long service life of the rolling body bearings, preferably such that the maintenance intervals at least correspond to or exceed the typical downtimes of the rotary drum. Also, these tests have demonstrated that ball joints of this type do not have a satisfactory service life.
Based on the above-mentioned circumstances, the invention is based on the objective of additionally improving the cleaning of the inner wall in the feed region in rotary drums of this type. According to another objective, the invention, aims to ensure a low-maintenance operation of the cleaning devices in rotary drums of the initially described type and, in particular, to improve the service life of the bearings used for the cleaning bodies.
According to the invention, this objective is attained with a rotary drum that is realized in accordance with a rolling body arrangement according to the present invention. In this respect, this result is achieved with a rotary drum that includes a rolling body arrangement for cleaning the interior of the drum, a stationary feed end for the material to be treated, a mounting device for mounting the rolling body arrangement on to the feed end of the rotary drum and a rotary bearing that allows the rolling body to roll on the inner side of the rotary drum wall and which connects the rolling body to the mounting device. The rotary drum further including an oblong scraping device which is arranged between the mounting device and the rotary bearing wherein the scraping device is mounted on the mounting device such that it is able to carry out a pendulum motion in at least one direction, but is unable to turn about itself. Furthermore, the end of the scraping device which is on the side of the rotary bearing is connected to the rotary bearing in such a way that it is able to carry out a pendulum motion in at least one direction (coordinate). The invention is based on the notion that the cleaning of the inner rotary drum wall can only be carried out in a truly efficient fashion in the region situated directly adjacent to the stationary feed end and in the ensuing region if an oblong scraping device is arranged between the pivot (rotary) bearing of the rolling body which rolls on the inner rotary drum wall, and the mounting device for the rolling body at the end wall on the feed side, wherein the oblong scraping device is able to carry out a pendulum motion, but unable to turn about itself. Due to this solution, the rolling body is provided with a substantial freedom of motion and constantly moved in the rotating direction by the rotating rotary drum in a particularly effective fashion, whereafter the rolling body rolls back in the direction of the rotary drum bottom. In this case, the rolling body carries out a significant pendulum motion transverse to the axis of the rotary drum. This results in a significantly improved transmission of power and motion on the end of the oblong scraping device which is situated distant from the feed side. This means that the scraping device carries out a very intense pendulum motion, during which the scraping device exerts correspondingly high cleaning forces upon the critical feed region of the rotary drum with its scraping strips. The arrangement according to the invention improves the cleaning effect in the feed region, as well as in the axial region of the rotary drum situated directly adjacent thereto, i.e., in the regions of the rotary drum in which the risk of deposits becoming caked and encrusted on the inner wall of the rotary drum is particularly high. The invention also makes it possible to withstand process temperatures up to 1150xc2x0 C.
According to a further aspect of the invention, the objective is attained with a rotary drum that includes a rolling body arrangement for cleaning the interior of the rotary drum. The rotary drum having a stationary feed end for the material to be treated and a mounting device for mounting the rolling body arrangement on to the feed end of the rotary drum. The rolling body arrangement having a rotary bearing which also includes a hinged or swivel bearing, such as a cardan or universal joint, that allows the rolling body to roll on the inner side of the rotary drum wall and connects the rolling body to the mounting device. The hinge or swivel bearing having coatings, linings or bearing bushings consisting of a self-lubricating material that is resistant to high temperature and/or corrosion, wherein the coatings, linings or bearing bushings have a cylindrical shape and/or the shape of an annular disc and which are arranged between the cooperating bearing surfaces of the rotary bearing as well as of the hinge or drag bearings respectively. It was recognized that a separation of axially and radially stressed bearing surface regions significantly improves the mobility of rolling and/or scraping cleaning bodies.
In order to also achieve the desired low-maintenance operation of the cleaning body bearings when carrying out chemical processes in the rotary drums at elevated temperatures, e.g., the carbonization of various substances such as oil residues, coal-tar asphaltums, chemical and other wastes and residues, the invention proposes to manufacture the coatings, linings or bearing bushings arranged between the axial and radial bearings surfaces of a self-lubricating material that is resistant to high temperatures and/or corrosion.
The invention makes it possible to achieve a significantly improved mobility of the cleaning bodies which results in a superior cleaning effect and a substantially longer service life of the cleaning body bearingsxe2x80x94namely also at elevated temperatures of, for example, between 600xc2x0 C. and 850xc2x0 C. such as occur during carbonization process in rotary drums. In addition to using graphite as the bearing coating, metal-impregnated graphite bearings, special graphite bearings or ceramic bearings may, in particular, be considered for this purpose,xe2x80x94as well known in the art per se. The hinge bearings and pivot bearings according to the invention may be designed such that sliding speeds up to approximately 10 m/s and specific surface loads up to approximately 3 N/mm2 can be tolerated. In this case, an excellent rotary motion, sliding motion and/or pivoting or pendulum motion of the cleaning bodies can be permanently ensured. The invention also makes it possible to withstand process temperatures up to 1150xc2x0 C. Further improvements include at least one hinge or swivel bearing arrangement, e.g., cardan or universal joints which includes pivot pins at right angles to one another and provides the pendulum motion of the scraping device. Even another advantage relates to utilizing the hinge or swivel bearing arrangement between the scraping device and the rolling body arrangement for the pendulum movement only and utilizing a rotary bearing for allowing the rolling body arrangement to turn about its axis. Further improvements relate to utilizing self-lubricating coatings, linings or bearing bushings between the cooperating bearing surfaces of the rotating bearings or of the universal joint or both. The self-lubricating coatings, linings or bearing bushings described above can consist of pure graphite, carbon-graphite, metal-impregnated graphite (e.g., with antimony, copper, bronze, nickel, silver, etc.) or of a ceramic material, e.g., silicon carbide, etc. Furthermore, utilizing coatings, linings or bearing bushings consisting of materials that are resistant to high temperatures and which are arranged between the cooperating bearing surfaces of the rotary bearing or of the universal joints, or both allows the device to be utilized in high temperature environments. The coatings, linings or bearing bushings can also consist of materials that are resistant to corrosion since these devices are used in harsh environments. In addition, the rotary bearing can contain a cantilever pin with axial and radial bearing surfaces and a bearing cage that surrounds the cantilever pin and which has corresponding axial and radial bearing surfaces for the cantilever pin. Furthermore, the cantilever pin can be carried by a frame or housing that surrounds the pin and the bearing cage.
The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.
Additional details, characteristics and advantages of the object of the invention are disclosed in the subclaims and the following description of the respective figuresxe2x80x94which in an exemplary fashionxe2x80x94show one preferred embodiment of the rotary drum according to the invention with a scraping body/cleaning body combination.